1. Field of the Invention
The present invention relates to a steering wheel for a vehicle that maintains a gap between a spoke and an airbag cover as small as possible when an airbag module for a driver is mounted on a steering wheel.
2. Description of Related Art
In general, a driver directly operates a steering wheel 1 to turn a vehicle. As shown in FIG. 1, the steering wheel includes a rim 10 that is formed at an outer peripheral portion, a hub 20 that is formed at a central portion, and a plurality of spokes 30 that connect hub 20 with rim 10.
A horn operation device and an airbag module for a driver are mounted on hub 20. The airbag module for a driver is covered with an airbag cover 40, which is fitted to hub 20, not to be exposed to the outside.
Meanwhile, due to the characteristics of an assembling structure of airbag cover 40, a predetermined gap G1 is formed between spoke 30 and airbag cover 40 as shown in FIG. 2.
It is preferable that gap G1 be as small as possible in consideration of appearance. After spokes 30 are completely manufactured, the gap of steering wheel 1 in the related art is increased as shown in FIG. 3, so that appearance quality deteriorates. For this reason, there is a problem in that customer complaints are increased.
That is, as shown in FIG. 2, each of spoke 30 of steering wheel 1 includes an armature member 31 that connects rim 10 with hub 20 and serves as a frame, an intermediate structure 32 that overlaps and is fixed to armature member 31, and a cover 33 that surrounds intermediate structure 32 and is fixed to the intermediate structure 32.
Armature member 31 is made of magnesium, and cover 33 is made of leather.
Furthermore, intermediate structure 32 includes a first intermediate member 321 that is made of polyurethane and overlaps and is fixed to armature member 31, and a second intermediate member 322 that is made of expanded polystyrene and overlaps and is fixed to first intermediate member 321.
In this case, first intermediate member 321 is hard, and second intermediate member 322 is soft.
After spokes 30 are completely assembled using the above-mentioned structure, steering wheel 1 is subject to a hot blast process that is a post-process and removes wrinkles of cover 33.
In the hot blast process, hot air of which temperature is in the range of 70 to 80° C. is applied to spokes 30 for a predetermined time in order to remove wrinkles of cover 33.
However, after steering wheel 1 is subject to the hot blast process as described above, cover 33 grows longer and the edge of soft second intermediate member 322 facing airbag cover 40 is deformed as shown in FIG. 3.
As a result, the gap formed between spoke 30 and airbag cover 40 is increased from a gap G1 (see FIG. 2) formed when a hot blast process is not performed, to a gap G2 (see FIG. 3) after a hot blast process is performed. Accordingly, there is a problem in that appearance quality deteriorates and customer complaints are increased.
The following structure has been proposed to prevent this. That is, as shown in FIG. 4, a protrusion 321a is integrally formed with the first intermediate member so as to protrude upward from an end of first intermediate member 321 facing airbag cover 40, and the second intermediate member is fitted to first intermediate member 321 so that an end of second intermediate member 322 comes in contact with protrusion 321a. 
The structure of FIG. 4 is proposed to prevent the edge of soft second intermediate member 322 from being deformed due to the hot blast process. When steering wheel 1 having the structure of FIG. 4 is deformed as shown in FIG. 5 due to a hot blast process, a gap G3 formed between spoke 30 and airbag cover 40 is significantly decreased due to hard first intermediate member 321 as compared to gap G2 of FIG. 3 in the related art. However, there is a problem in that gap G3 is still larger than gap G1 of FIG. 4 when a hot blast process is not performed.
That is, even though being made of hard polyurethane, first intermediate member 321 is deformed due to shrink of cover 33 which is made of leather during a hot blast process. For this reason, if heat is applied to the first intermediate member during the hot blast process, the edge of the first intermediate member facing airbag cover 40 is deformed. Accordingly, the gap formed between spoke 30 and airbag cover 40 becomes larger after the hot blast process as compared to before the hot blast process.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.